Signaling by electromagnetic waves.



R. A. FESSENDEN.

SMNAL'ING BY ELECTROMAGNETIC WAVES.

' PPLICIATION FILED JULY 8-. 1903.

2 SHEETS-SHEET I.

m RESONANCE EFFECT Fmzgusrvclcs L mmzm Patented Ma 30, 1916.

R. A. FESSENDEN.

SIGNALING BY ELECTROMAGNETIC WAVES. 7

APPLICATION FILED JULYB. 1-903.

Patented Ma 30,1916.

2 SHEETS-SHEET 2.

. ances in the transmission of telegraphic mes- Tt'also bears a particular Lite ASSIGNBTENT$, T0 SAMUEL In". YJEN'JLNER,

01F lPITTSBURG-H, PENNSYLVANIA, AND

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SIG-N BY ELECTROMEAGNETIC- VVAVTJS.

Specification of Letters Patent.

Application filed July 8, 1903. serial No. 164,738.

To all whom 2'21 may concern.

Be it known that I, REGINALD A. Fnssnn- DEN, residing at Fortress Monroe, in the county of Elizabeth City and State of Virginia, a citizen of the United States, have invented or discovered certain new and use ful Improvements in Signaling by Electromagnetic Waves, of which improvements the following is a specification. v The invention described herein relates to methods for securing freedom from disturbsages, whether such disturbances originate'in the stations, from outside stations or from atmospheric disturbances.

The invention has a particular relation to the method in which conductors are shown so arranged as to equalize'each others eflect as regards disturbing impulses while permitting signals to be received when of the de sired periodicity.

tems in which prolonged trains of waves are emitted and received and indications produced at the receiving station by a cumulatively acting receiver situated in a closed tuned circuit and tuned to group frequencies as well as wave frequencies.

One of the most important problems in signaling by'electro magnetic waves is the matter of interruption from disturbing sources. This disturbance cannot be cut out by simply tuning the circuits to a wave frequency, as applicant has discovered. Assume for example, that two stations are capable of working over a distance of one huni dred miles and are located about a quarter of a mile away from each other. Since the energy varies as the square of the distance,

to 160,000 times as much energy will be received from one stationby the, neighboring station,

as is receivedby the station to which the message is being-sent. It is evident therefore that the resonant rise must be in the neighborhood of 500,000 in order to prevent disturbances. Such a very large resonant rise cannot be obtained, as it would necessitate an absolutely infinitesimal amount of dampening. in the receiving circuit, and

, would moreover notpermit of rapid telegraphy as the trains of waves would have to persist over a large fraction of a second.

This appl cant proposes to use more than receiving clrcuit, whereby dlsturblng,

relation to sysstations rise, one

impulses may he made to neutralize each other. This method while well adapted for its purpose, does not give complete neutralization-where a large number of stations withinrange of each other are operated at frequencies approximating that of the station, whose resonant point is located by the maximum ordinate 14 of the curve, at the points A, E, Figure. l, where the ordinates U, D, repres'entthe efle'cts produced'by disturbing impulses and the abscissae w y represents frequencies. j

lltwill be seen that the ordinate C is slightly larger than the ordinate l) and hence the neutralization will not be complete. To be made complete for this periodicity the effect of one of the conductors must be greater than that of the other. In this case a disturbing impulse whose periodicity is lower than the periodicity indicated by C and D, will effect a conductor tuned to l) more than one tuned to C, since the. maxi mum point is now to the right and consequently the conductors will fail to neutralize each'other. My method overcomes the di'fficulties, especially where a large number of are being used in closeproximity. In the accompanying drawings forming apart of this specification, Fig. 1 is a graphic'showing of resonance efi'ects. Figs; 2 and 3 are diagrams of two difi'erent specific forms of selective recelving systems Fig. 4.- is a diagram of transmitters. Fig. 5 is a longitudinal section of an adjustable transformer Themethod shown herein is based uponthe fact that resonant curves have in general a curvature which is always .of the same sign, and hence by the use of three circuits all very strongly tuned and with very small dampening so as to allow larger resonant circuit tuned to the period at which it is desired to receive, one tuned to a '1i 'her eriod and the other to a lower pcriod, the higher and lower circuits may be made to neutralize the effectof disturbing impulses produced on the receiver by the properly tuned circuit.

For example, if in Patented May 30, rare.

F T tected from disturbances in accordance wlth the principles of my invention.

9. If the circuits corresponding to 4 and 6 be proportioned whether by trial or calculation or both combined, so as to neutralize the efiect produced on the conductor tuned to periodicity 5, then no disturbing signals will be received. If, however, the periodic disturbance which it is desired to receive and whose frequency is located by the ordinate 11, is impressed on three circuits whose natural periods are indicated by the abscissae'of the ordinates 10, 11 and 12 so that the eriodic disturbance is in resonance with 11, 1t will be seen that the effects produced are proportioned to the ordinates 13, 14, and

15 and that the effect on the proper circuit will not be neutralized and in fact not affected to any great extent, so that a strong signal will be produced. It is found that the neutralization will be complete no matter if the disturbing impulse is higher or lower than that at which it is desired to receive, and that at all points except at points very close to the resonant point, neutralization may be practicallycomplete, es pecially if the lower or higher circuits be. dampened as by eddy-current losses or resistance losses to a higher degree than the middle one. All circuits however, should be strongly oscillatory.

Where it is desired to make the selectivity still more pronounced it is preferred to use a receiver tuned to group frequencies as well as to wave frequencies and by this combination entire freedom from all disturbances is obtained and it is possible to work any desired number of stations in close proximity to each other.

In Fig. 2, showing one arrangement for accomplishing the desired result, the three receiving conductors, 16, 17 and 18, are tuned, 17 to the proper periodicity at which it is desired to receive, 16 to a higherpe-- riodicity and 18 to a lower periodicity. Coils 19, 20 and 21 are used for tuning but they are preferably arranged as by putting in resistance so as to avoid unduly prolonging the oscillations of the conductors for this would cause a loss of efliciency when acting as a receiving conductor, The re- -ceivers 22, 23 and 24 are preferably of the current operated type. An indicating mechanism 32, 32, such. as a telephone is oper-' ated by the current in the local circuits 25,.' 26 and 27 causing the coils 28, 29-, 30 and 31 to vary when the receivers 22, 23 and 24 are operatiyely affected by electro-magnetic waves. That is, the coils 30 and 31 act in the same direction on the magnet 32, but togetheract in opposition to coils 28 and 29. The latter coils acting together, the effect is so diminished that when the disturbing eifects on the three antenna are thesam e, the resulting effect on magnet 32 is practically reduced to zero. 'This can be accomplished by either making thecoils 30 and 31 slightly weaker than the coils 28 and 29,

or by adjustment of the sources of voltage in the circuits 25, 26 and 27. In operation a disturbing impulse striking all three conductorswill', if it is not in tune, produce very closely equal effects on thereceivers 22, 23 and 24. Hence as is shown, these effects will neutralize-each other as regards the indicating mechanism 32 and no indication will be produced. On the other hand, if the oscillations are tuned to the proper periodicity the receiver 23 ,will be effected much more strongly than 22 and 24 and anindication will be produced. For many purposes instead of grounding the conductors 16, 17 and 18 the portion of the conductors beyond the receivers 22, 23 and 24 may be constructed as by lengthening them so as to be electrical equivalents of the portions of the conductors above the receivers. A single vertical and several branch circuits may be employed in lieu of the .three separate verticals. Three branches, 34, 35 and 36 extend from the vertical 59, which is connected to ground.

In Fig. 3 the circuit comprising the vertical 59, with its adjustable inductance 63 and branch circuit 35 and its connection to ground is resonant to the proper periodicity, while the circuit comprising vertical 59, and its connection to ground through the branch circuit 34 is resonant to a higher periodicity, the circuit comprising vertical 59 and its connection to ground through the branch circuit 36 is resonant to a lowenperiodicity ,than that of the circuit comprising vertical 59 and its connection to ground through branch circuit 35. The inductances in the branches 34, 35 and 36 form primaries of transformers, whose secondaries, 37, 38 and 39 are in circuitwith the primaries 40, 41, 42, whose secondaries 43, 44 and- 45 are preferably in series with each other. Capacities 46 and 47 and 48 may be inserted in the transformer circuits as shown and the capacity 49 may be inserted in the circuit to ground of the receiving conductor. I prefer to use an additional tuning inductance 63, in addition to the other tuning means. A

' capacity 50 may be inserted in the secondary 44. A receiver 77 preferably of the current operated type, as for example a magnetic receiver as in Fig. 7 may be substituted for receiver 57. The position of the receiver -57 and the capacity 50 may be interchanged. The indicating mechanism 52, as a telephone,

is preferably adapted to respond to only one frequency. 53 is the local resistance for source of voltage.

adjusting the local voltage by shunting more or less of the resistance 53, and 54 is the local This method of adjusting the local voltage in the local circuits 25, 26 and 27 Fig. 2. The circuit 43, 57, 45, 44, is preferablytuned to the-periodicity of the circuit 59, 35, 49, '55. A ring of nickel, or a resistance 56 is so arranged as to produce an adjustable amount of dampening in oscillatory.

The operation of the'combination shown in Fig. 3 is similar to that shown in Fig. 2, the general character of the results produced being effected by use of branch circuits and transformers instead of single circuits without transformers although in general the ac tion is more complete and efficient. As in the construction shown in Fig. 2, a disturbing impulse which is not of a proper periodicity, produces impulses in the branch circuits which are neutralized and do not produce indications in the indicators or the indicating mechanism, while a-perlodlc'impulse in resonance to the circuit 33, 35, 49, 55, does produce anlindication, Thus, disturbing impulses received by antenna 59 produce effects in coils 43 and 45 which, taken together, present an equal and opposed effect to that produced in izing the effect on the receiver 57.

In the method of sending as shown in Fig. 4, the sending conductor .59, 57, is grounded. An inductance 57 is used for tuning. A self-inductance 60 is arranged in the circuit of the source of voltage, which is preferably constant. A. key. 62 is employed for cutting in and out a portion of the inductance 57 and hence operates to change the periodicity o'f'the sending oscillations.

n operation, the source of voltage 61 charges the sending conductor until the dis charge passes across the gap 58, which may e formed of a mercury lai p. The presence of inductances 60 and 57 and the capacity ofthe vertical wire 59 causes high frequency oscillations to be generated, whose frequency is determined by the electrical .constants of the. circuits. in F ig.'4 an ohmic-resistance with small selfinductance may be substituted.

In Fig. 5 is shown the method of arrang ing the sets of primaries jand secondaries,

for example, the set The primary 34 and secondary 43 are wound at opposite ends of the glass tube 65 and the secondary 37 and primary 40 on opposite ends of the glass. tube 65, but fartherapartthan'thecoils 3'4 an'd 43. This glass tube 65 tube 65 on which the-coils 34 and 43 are wound. Any suitable means may be employed for effecting the adjustment of. the

is similar to that shownthe circuits 37, 40, 46 and 39, 42, 48, while still leaving them strongly bration of the soft coil 44, thereby neutral- Iniplace of the inductance 60.

including the primary v 34, 40 and the secondaries 37, 43in Fig. 3.

are also wound broad method claimed by combining the effects produced on conducis arranged to slide within'the- W" Salt glass tubes as for example, the tube 65 may be carried by a threaded rod passing through a yoke on the tube 65, and provided with the milled head 66, whereby the screw may be rotated to effect the adjustment of the inner tube 65. A capacity 46 may be arranged as Fig. 6 consisting of a permanent magnet- .68 having similar poles 69 and 70. A soft iron strip 71 is so arranged as to be capable of vibrating to and fro between, the

poles 69 and and is connected by a wire 73 to a diaphragm 72. A weight 74 is mounted on the upper end of the soft iron strip so as to be capable of adjustment, whereby to vary the natural period of viiron strip; The coil; -75 of the telephone is wound as shown on the vibrating strip ranged in suitable relation to the diaphragm 72. On the passage of a fluctuating current through the coil 75 the soft iron and a resonator 76 is ar-,

strip is caused to oscillate backward and for-P ward, hence to produce a note which is reinforced or augmented by the resonator.7 6.

Fig. 7 shows another form of receiver which.

is tuned both electrically and mechanically.

The diaphragm 77 preferably formed of thin mica or glass, has an arma ure 78 ce mented thereto, the of very thin iron wire. formed of thin iron and s0, s1, 82', is

carrying the circuit armature bemg formed A small magnet 79,

arranged in suitable relation.

to the armature and diaphragm. The resonator 83 is arranged as, descr bed in Fig. 6.

The diaphragm the form of, a strip, and'is preferably made 77 may" be constructed in.

to have a natural period of oscillation ldeH'm tical with that.

of the resonator 83. When desired, the resonator 83 may be omitted; 71

\Vhen used the'resona'tor the particular form of, apparatus described herein as the ineconsists 1n tors tuned to pferiodicities both above and 83 should be tuned 'to the grou 'o, frequency as should also be the diaphragm is preferably below the per odicity of-the conductor or conductors 'WlllCll ,are tuned :to -the waves which it is dgesircd to receive, with the effectproduced on the latter conductor or conduo the vertical and as near to the surface of the ground as possible. This avoids the runningof leads into the office which fre-.

quently acts to cut down the radiation to a very appreciable extent and to prevent sharp tuning, The leads from the lower end of the spark gap to ground are made to have relatively large capacity and small inductance. The effect of employing neutralizing conductors on each side of the resonant point is advantageous in that as is well known from the paper on Fluorescence in Stokes Collectedfdyiers, (see also J. J. Thomsons Recentl'fi'searches in Electricity and Zl1'agnet2'sm'ffl893 paragraph 327, page 390- and paragraph e32, page 533,) resonant systems in-whijehthe vibrations are not forced tend-.toaffec't each other, and hence if. the conductors are both of a higher or both of.-a lowerperiodicity than that of the receiving. wire proper, the receiving .wire tends to be pulled out of resonance,

while by the use of .wires on each side the effect is very much smaller and may be also completely neutralized. This matter of preventing interference is especially suited to station using the method of sending by'thro'wing it in and out of tune, as in this case, if the neutralization is not absolutely complete. the sending of a signal does "not produce the full amount of disturbancey lout only adifierential effect, that is, the .di-fierence in neutralization which would b, produced by shifting the point of resonance slightly to the left or right. This/is illustrated in F'g. 8, where the curve slibwn in the :full li'ue represents the position of the resonance curve. abscissa. beiifg firequency and ordinatesbeing int en's? A when the sending key is down, and h-e resonance curve shown in the dotted liI ie being the p sition. of the resonance curve when the keyfis up. The lines 8% and 85 show the positions of the maximum po nts of these curves and lines 86 and 87 indicate by their length from the base line to the point at which they c'ut the curve. the intensity'chan'ge of position of the resonant point.

It is preferred to vuse the larger induc tions, as this tends to keep the intensity of received waves more nearly the same, and gives a general method and system which separates the tunes, which are apt to be received.

1. In electric signaling, the method of neutralizing disturbing influences on a receiver, which consists in opposing to the effect'of such influences on a circuit resonant to the signaling frequency the effect of such influences upon a circuit resonant to a different frequency. 2. The method of annulling disturbing influences in a receiving circuit for electromagnetic waves'by providing two supplementary receiving circuits and causing them to neutralize all effect on the receiver when the frequency is not that desired.

3. In signa ing by electromagnetic Waves, the method ,iwhich comprises transferring the energy from one circuit to another by transformer: action,f. fandvarying the relative position of the-primary and; secondary to adjust the tuning-of the primary and secondary .c'rcuits to" various couplings correspondingl to the character .o'f,disturb'ing impulses received. v

4., In signaling by electromagnetic waves, the method whichcomprises counterbalancing the effects of'distfurbing impulses on a receiver by transferring the energy by transformation to several branch circuits, and ,n eantime adjusting both the tuning and the ratio;.of coupling of said circuits according to the-character of disturbing impulses, and combiningthe effects on a receiver.

5 In signaling by electromagnetic waves, the method which comprises balancing the effects of disturbing received impulses in branchil'ciruits by adjusting their tune, transferring the energy of all impulses into other circuits'by transformation, adjusting the ratio of transformation according to the character of disturbing impulses, and combinriig the effects on a receiver.

,., (i i, In'signaling by electromagnetic waves,

-"tli'e -method which comprises balancing the efl'ectsonca receiver of branch circuits by trapsferring the energy of said circuits by transferma tion into other circuits, adjustin'g iflie'ratio of transformation, and combiningtl fe effects on a receiver.

my as? c REGINALD a. FESSENDEN.

VVit-nesses:

Gnoncn M. CornNnAvnR, W. DE LACY.

In testlmony whereof, I have hereunto set 

